Chemokines constitute a family of cytokines that are produced in inflammation and regulate leukocyte recruitment (Baggiolini, M. et al, Adv. Immunol., 55: 97-179 (1994); Springer, T. A., Annual Rev. Physio., 57: 827-872 (1995); and Schall, T. J. and K. B. Bacon, Curr. Opin. Immunol, 6: 865-873 (1994)). Chemokines are capable of selectively inducing chemotaxis of the formed elements of the blood (other than red blood cells), including leukocytes such as neutrophils, monocytes, macrophages, eosinophils, basophils, mast cells, and lymphocytes, such as T cells and B cells. In addition to stimulating chemotaxis, other changes can be selectively induced by chemokines in responsive cells, including changes in cell shape, transient rises in the concentration of intracellular free calcium ions ([Ca2+]i), granule exocytosis, integrin upregulation, formation of bioactive lipids (e.g., leukotrienes) and respiratory burst, associated with leukocyte activation. Thus, the chemokines are early triggers of the inflammatory response, causing inflammatory mediator release, chemotaxis and extravasation to sites of infection or inflammation.
Chemokines are related in primary structure and share four conserved cysteines, which form disulfide bonds. Based upon this conserved cysteine motif, the family can be divided into distinct branches, including the C—X—C chemokines (α-chemokines) in which the first two conserved cysteines are separated by an intervening residue (e.g., IL-8, IP-10, Mig, I-TAC, PF4, ENA-78, GCP-2, GROα, GROβ, GROδ, NAP-2, NAP-4), and the C—C chemokines (β-chemokines), in which the first two conserved cysteines are adjacent residues (e.g., MIP-1α, MIP-1β, RANTES, MCP-1, MCP-2, MCP-3, I-309) (Baggiolini, M. and Dahinden, C. A., Immunology Today, 15: 127-133 (1994)). Most CXC-chemokines attract neutrophil leukocytes. For example, the CXC-chemokines interleukin-8 (IL-8), GRO alpha (GROα), and neutrophil-activating peptide 2 (NAP-2) are potent chemoattractants and activators of neutrophils. The CXC-chemokines designated Mig (monokine induced by gamma interferon) and IP-10 (interferon-gamma inducible 10 kDa protein) are particularly active in inducing chemotaxis of activated peripheral blood lymphocytes.
CC-chemokines are generally less selective and can attract a variety of leukocyte cell types, including monocytes, eosinophils, basophils, T lymphocytes and natural killer cells. CC-chemokines such as human monocyte chemotactic proteins 1-3 (MCP-1, MCP-2 and MCP-3), RANTES (Regulated on Activation, Normal T Expressed and Secreted), and the macrophage inflammatory proteins 1α and 1β (MIP-1α and MIP-1β) have been characterized as chemoattractants and activators of monocytes or lymphocytes, but do not appear to be chemoattractants for neutrophils.
A chemokine receptor that binds the CXC-chemokines IP-10 and Mig has been cloned, characterized (Loetscher, M. et al., J. Exp. Med., 184: 963-969 (1996)) and designated CXCR3. CXCR3 is a G-protein coupled receptor with seven transmembrane-spanning domains and has been shown to be restrictively expressed in activated T cells, preferentially human Th1 cells. On binding of the appropriate ligand, chemokine receptors transduce an intracellular signal through the associated G-protein resulting in a rapid increase in intracellular calcium concentration.
The CXCR3 receptor mediates Ca2+ (calcium ion) mobilization and chemotaxis in response to IP-10 and Mig. CXCR3 expressing cells show no significant response to the CXC-chemokines IL-8, GROα, NAP-2, GCP-2 (granulocyte chemotactic protein-2), ENA78 (epithelial-derived neutrophil-activating peptide 78), PF4 (platelet factor 4), or the CC-chemokines MCP-1, MCP-2, MCP-3, MCP-4, MIP-1α, MIP-1β, RANTES, I309, eotaxin or lymphotactin. Moreover, a third ligand for CXCR3, I-TAC (Interferon-inducible T cell Alpha Chemoattractant), has also been found to bind to the receptor with high affinity and mediate functional responses (Cole, K. E. et al., J. Exp. Med., 187: 2009-2021 (1998)).
The restricted expression of human CXCR3 in activated T lymphocytes and the ligand selectivity of CXCR3 are noteworthy. The human receptor is highly expressed in IL-2 activated T lymphocytes, but was not detected in resting T lymphocytes, monocytes or granulocytes (Qin, S. et al., J. Clin. Invest, 101: 746-754 (1998)). Additional studies of receptor distribution indicate that it is mostly CD3+ cells that express CXCR3, including cells which are CD95+, CD45RO+, and CD45RAlow, a phenotype consistent with previous activation, although a proportion of CD20+ (B) cells and CD56+ (NK) cells also express this receptor. The selective expression in activated T lymphocytes is of interest, because other receptors for chemokines which have been reported to attract lymphocytes (e.g., MOP-1, MCP-2, MCP-3, MIP-1α, MIP-1β, RANTES) are also expressed by granulocytes, such as neutrophils, eosinophils, and basophils, as well as monocytes. These results suggest that the CXCR3 receptor is involved in the selective recruitment of effector T cells.
CXCR3 recognizes unusual CXC-chemokines, designated IP-10, Mig and I-TAC. Although these belong to the CXC-subfamily, in contrast to IL-8 and other CXC-chemokines which are potent chemoattractants for neutrophils, the primary targets of IP-10, Mig and I-TAC are lymphocytes, particularly effector cells such as activated or stimulated T lymphocytes and natural killer (NK) cells (Taub, D. D. et al., J Exp. Med., 177: 18090-1814 (1993); Taub, D. D. et al., J Immunol, 155: 3877-3888 (1995); Cole, K. E. et al., J. Exp. Med., 187: 2009-2021 (1998)). (NK cells are large granular lymphocytes, which lack a specific T cell receptor for antigen recognition, but possess cytolytic activity against cells such as tumor cells and virally infected cells.) Consistently, IP-10, Mig and I-TAC lack the ELR motif, an essential binding epitope in those CXC-chemokines that efficiently induce neutrophil chemotaxis (Clark-Lewis, I. et al., J. Biol. Chem. 266: 23128-23134 (1991); Hebert, C. A. et al., J. Biol. Chem., 266: 1989-18994 (1991); and Clark-Lewis, 1. et al., Proc. Natl. Acad. Sci. USA, 90: 3574-3577 (1993)). In addition, both recombinant human Mig and recombinant human IP-10 have been reported to induce calcium flux in tumor infiltrating lymphocytes (TIL) (Liao, F. et al., J Exp. Med., 182:1301-1314 (1995)). While IP-10 has been reported to induce chemotaxis of monocytes in vitro (Taub, D. D. et al., J. Exp. Med., 177: 1809-1814 (1993), the receptor responsible has not been identified), human Mig and I-TAC appear highly selective, and do not show such an effect (Liao, F. et al., J. Exp. Med., 182: 1301-1314 (1995); Cole, K. E. et al., J. Exp. Med., 187: 2009-2021 (1998)). IP-10 expression is induced in a variety of tissues in inflammatory conditions such as psoriasis, fixed drug eruptions, cutaneous delayed-type hypersensitivity responses and tuberculoid leprosy as well as tumors and in animal model studies, for example, experimental glomerulonephritis, and experimental allergic encephalomyelitis. IP-10 has a potent in vivo antitumor effect that is T cell dependent, is reported to be an inhibitor of angiogenesis in vivo and can induce chemotaxis and degranulation of NK cells in vitro, suggesting a role as a mediator of NK cell recruitment and degranulation (in tumor cell destruction, for example) (Luster, A. D. and P. Leder, J. Exp. Med., 178: 1057-1065 (1993); Luster, A. D. et al., J. Exp. Med. 182: 219-231 (1995); Angiolillo, A. L. et al., J. Exp. Med., 182: 155-162 (1995); Taub, D. D. et al., J. Immunol., 155: 3877-3888 (1995)). The expression patterns of IP-10, Mig and I-TAC are also distinct from that of other CXC chemokines in that expression of each is induced by interferon-gamma (IFNδ), while the expression of IL-8 is down-regulated by IFNδ (Luster, A. D. et al., Nature, 315: 672-676 (1985), Farber, J. M., Proc. Natl. Acad. Sci. USA, 87: 5238-5242 (1990); Farber, J. M., Biochem. Biophys. Res. Commun., 192 (1): 223-230 (1993), Liao, F. et al., J. Exp. Med., 182: 1301-1314 (1995); Seitz, M. et al., J. Clin. Invest. 87: 463-469 (1991); Galy, A. H. M. and H. Spits, J. Immunol., 147: 3823-3830 (1991); Cole, K. E. et al., J. Exp. Med., 187: 2009-2021 (1998)).
Chemokines are recognized as the long-sought mediators for the recruitment of lymphocytes. Several CC-chemokines were found to elicit lymphocyte chemotaxis (Loetscher, P. et al., FASEB J., 8: 1055-1060 (1994)), however, they are also active on granulocytes and monocytes (Uguccioni, M. et al., Eur. J. Immunol., 25: 64-68 (1995); Baggiolini, M. and C. A. Dahinden, Immunol. Today, 15: 127-133 (1994)). The situation is different for IP-10, Mig and I-TAC, which are selective in their action on lymphocytes, including activated T lymphocytes and NK cells, and which bind CXCR3, a receptor which does not recognize numerous other chemokines and which displays a selective pattern of expression.
In view of these observations, it is reasonable to conclude that the formation of the characteristic infiltrates in inflammatory lesions, such as, for example, delayed-type hypersensitivity lesions, sites of viral infection and certain tumors is a process mediated via CXCR3 and regulated by CXCR3 expression. Lymphocytes, particularly T lymphocytes, bearing a CXCR3 receptor as a result of activation can be recruited into inflammatory lesions, sites of infection and/or tumors by IP-10, Mig and/or I-TAC, which can be induced locally by interferon-gamma. Thus, CXCR3 plays a role in the selective recruitment of lymphocytes, particularly effector cells such as activated or stimulated T lymphocytes. Accordingly, activated and effector T cells have been implicated in a number of disease states such as graft-rejection, inflammation, rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease and psoriasis. Thus, CXCR3 represents a promising target for the development of novel therapeutics.
Reference is made to PCT Publication No. WO 93/10091 (Applicant: Glaxo Group Limited, Published May 27, 1993) which discloses piperidine acetic acid derivatives as inhibitors of fibrinogen-dependent blood platelet aggregation having the formula:

An illustrative compound of that series is:

Reference is also made to PCT Publication No. WO 99/20606 (Applicant: J. Uriach & CIA. S. A., Published Apr. 29, 1999) which discloses piperazines as platelet aggregation inhibitors having the formula:

Reference is also made to US Patent Application No. US 2002/0018776 A1 (Applicant: Hancock, et al. Published Feb. 14, 2002) which discloses methods of treating graft rejection.
Reference is also made to PCT Publication No. WO 03/098185 A2 (Applicant: Renovar, Inc., Published Nov. 27, 2003) which discloses methods of diagnosing and predicting organ transplant rejection by detection of chemokines, for example, CXCR3 and CCL chemokines in urine.
Reference is also made to PCT Publication No. WO 03/082335 A1 (Applicant: Sumitomo Pharmaceuticals Co. Ltd., Published Oct. 9, 2003) which discloses methods of screening a CXCR3 ligand and methods of diagnosing type 2 diabetes by detecting the expression dose of a CXCR3 ligand in a biological sample.
Reference is also made to PCT Publication No. WO 02/085861 (Applicant: Millennium Pharmaceuticals, inc. Published Oct. 31, 2002) which discloses imidazolidine compounds and their use as CXCR3 antagonists having the formula:

An illustrative compound of that series is:

Reference is also made to PCT Publication No. WO 03/101970 (Applicant: SmithKline Beecham Corporation, Published Dec. 11, 2003) which discloses imidazolium compounds and their use as CXCR3 antagonists having the formula:

An illustrative example of that series is:

Reference is also made to US Patent Application No. US 2003/0055054 A1 (Applicant: Medina et al, Published Mar. 20, 2003) and related U.S. Pat. No. 6,794,379 B2 (Applicant: Medina et al, Published Sep. 21, 2004) which discloses compounds with CXCR3 activity having the formula:

An illustrative compound of that series is:

Reference is also made to U.S. Pat. No. 6,124,319 (Applicant: MacCoss et al., issued Sep. 6, 2000) which discloses compounds useful as chemokine receptor modulators having the formula:

Reference is also made to PCT Publication WO 03/070242 A1 (Applicant: CELLTECH R&D limited, Published Aug. 28, 2003) which discloses compounds useful as “chemokine receptor inhibitors for the treatment of inflammatory diseases” having the formula:

Reference is also made to PCT Publication WO 04/074287 A1, WO 04/074273 A1, WO 04/74278 (Applicant: AstraZeneca R & D Published Feb. 19, 2004) which discloses pyridine derivatives, processes for their preparation and use in the modulation of autoimmune disease, having the formula:
where R3 is phenyl, or a 5- or 6-membered aromatic ring with 1 or more nitrogen atoms.
Reference is also made to U.S. Patent Application Publication US 2006/0036093 A1, published Feb. 16, 2006, which refers to certain pyrimidone compounds binding to CXCR3 receptors.
There is a need for compounds that are capable of modulating CXCR3 activity. For example, there is a need for new treatments and therapies for diseases and conditions associated with CXCR3 such as inflammatory conditions (psoriasis and inflammatory bowel disease), autoimmune disease (multiple sclerosis, rheumatoid arthritis) and graft rejection (allograft and zenograft rejections for example) as well as infectious diseases, cancers and tumors, fixed drug eruptions, cutaneous delayed-type hypersensitivity responses, type I diabetes, viral meningitis and tuberculoid leprosy.
There is a need for methods of treatment or prevention or amelioration of one or more symptoms of diseases and conditions associated with CXCR3. There is a need for methods for modulating CXCR3 activity using the compounds provided herein.